The present disclosure relates to an image forming apparatus with an endless belt to which a toner image is to be transferred and particularly to a technique for controlling a meandering correction of the endless belt.
A color printer as an example of an image forming apparatus includes tandemly arranged image forming units of respective colors and an intermediate transfer belt (endless belt) to which toner images formed by these image forming units are to be primarily transferred. The intermediate transfer belt is driven and rotated and the toner images are successively transferred to a circumferential surface of the intermediate transfer belt in a superimposed manner in the image forming units of the respective colors, whereby a full color toner image is carried. This full color toner image is secondarily transferred to a sheet in a secondary transfer unit.
The intermediate transfer belt may move to meander or shift in a belt width direction perpendicular to a rotating direction while being driven and rotated. Such meandering or shifting causes transfer positions of toner images to the circumferential surface of the intermediate transfer belt to vary, thereby causing image defects such as color shift. Accordingly, a technique for correcting the meandering and shifting of a transfer belt is necessary.
There is known a meandering correction technique in which one of rollers on which an intermediate transfer belt is mounted is used as a meandering correction roller capable of adjusting an angle of inclination and the angle of inclination of the meandering correction roller is set according to a meandering amount of the belt. In this technique, the meandering amount of the intermediate transfer belt is grasped by monitoring a displacement of an edge position of this belt. For this monitoring, an optical or contact displacement sensor is arranged at an end part of the belt in a width direction.